Radio access schemes and radio networks (hereinafter referred to as “Long Term Evolution (LTE)” or “Evolved Universal Terrestrial Radio Access (EUTRA)”) of cellular mobile communication have been examined in 3rd Generation Partnership Project (3GPP). In LTE, an Orthogonal Frequency Division Multiplexing (OFDM) scheme is used as a downlink communication scheme. In LTE, a Single-Carrier Frequency Division Multiple Access (SC-FDMA) scheme is used as an uplink communication scheme. In LTE, a base station device is referred to as an evolved NodeB (eNodeB) and a terminal device is referred to as a User Equipment (UE). LTE is a cellular communication system in which a plurality of areas covered by base station devices are arranged in a cell form. A single base station device may manage a plurality of cells.
LTE corresponds to Time Division Duplex (TDD). LTE adopting a TDD scheme is referred to as TD-LTE or LTE TDD. TDD is a technology for enabling full duplex communication in a single frequency band by performing time division multiplexing on an uplink signal and a downlink signal. LTE corresponds to frequency division duplex (FDD).
In TD-LTE, a traffic adaptation technology and an interference reduction technology (DL-UL Interference Management and Traffic Adaptation) for changing a ratio of an uplink resource to a downlink resource according to an uplink traffic and a downlink traffic have been examined. When the traffic adaption technology is applied, a throughput can be considerably improved in radio communication systems more than when a ratio of an uplink resource to a downlink resource is not changed.
NPL 1 proposes a method of using a flexible subframe as a method of realizing traffic adaptation. A base station device can transmit a downlink signal or can receive an uplink signal with a flexible subframe. A terminal device regards a flexible subframe as a downlink subframe unless the terminal device is instructed to transmit an uplink signal by the base station device. Here, the traffic adaptation technology is also referred to as dynamic TDD.
NPL 1 describes that a Hybrid Automatic Repeat reQuest (HARQ) timing corresponding to a Physical Downlink Shared CHannel (PDSCH) is decided based on a newly introduced uplink-downlink configuration (UL-DL configuration) and a HARQ timing corresponding to a Physical Uplink Shared CHannel (PUSCH) is decided based on a first uplink-downlink configuration.
NPL 2 describes that (a) an uplink-downlink reference configuration (UL/DL Reference Configuration) is introduced and (b) several subframes can be scheduled for either uplink or downlink in accordance with dynamic grant/assignment.